Processing by multiple virtual machines may be performed on one physical machine. There is technology for estimating the power consumption of virtual machines performing processing on a physical machine, based on the usage ratio of central processing units (CPUs) of the virtual machines.
The usage ratio of each CPU is calculated based on how much time the CPU is occupied by processing for a program. In contrast, there is technology that varies an operating frequency (clock frequency) used to synchronize a circuit in accordance with a property such as the processing load of a CPU; in order to reduce the power consumed and heat radiated by the CPU. When control to vary the operating frequency of a CPU is performed, the actual number of operations per unit time of the CPU becomes different before and after the operating frequency is varied. Because power is consumed when the CPU operates, if the operating frequency of the CPU varies and the number of operations per unit time of the CPU changes, the power consumption of the CPU also varies. A related art method that estimates power consumption in accordance with the time that a CPU is occupied does not take into consideration changes in power consumption due to variation of the operating frequency. Thus, for a program that is to be executed, if the amount of time in which a CPU is occupied is the same before and after the operating frequency is varied, although the actual number of operations of the CPU varies, power consumption before and after the variation is mistakenly estimated to be the same.